1. Field of the Invention
The present invention relates to a 1-amino-2-cyclohexene derivative useful as an intermediate in the production of various medicines and agricultural agents and a production process therefor.
2. Discussion of the Background
Recently, condensed ring compounds containing hetero atoms (such as oxygen, nitrogen and sulfur) have been found to have various biological activities and vigorous developments have been made for them as medicines and agricultural agents. For example, Amemiya et al. have reported a dihydrobenzothiophene derivative or a tetrahydrobenzothiophene derivative having an inhibitory action on thromboxane synthetase (Journal of Medicinal Chemistry, 1989, vol. 32, pp. 1265-1272). Nagai et al. have reported a carbazole-3,4-dicarboximide derivative having anti-tumor activity (Japanese Patent Laid-Open No. 4-178387). Additionally, Dubroeucg et al. have reported a benzofuran or a benzothiophene carboxamide which has an effect as a tranquilizer, anti-anginal drug and immunomodulator (Japanese Patent Laid-open No. 63-39874).
Various studies have also been made for production processes for the condensed ring compounds. For condensed ring forming reactions, one method of bonding together the side chains of cyclic compounds having two side chains is the Robinson annelation. For example, Amemiya et al. obtain 4,5-dihydrobenzo[b]thiophene-6-carboxylic acid methyl ester by forming 7-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene using 3-bromothiophene as a starting material (MacDowell et al., Journal of Heterocyclic Chemistry, 1965, vol. 2, pp. 44-48), methoxycarbonylating the same, reducing the ketone and then dehydrating with an acid. Further, in the method of Nagai et al., a carbazole skeleton is formed according to the Fisher indole synthesis using N-benzyl-4-oxocyclohexane-1,2-carboximide as the starting material and then reacting the same with phenylhydrazine. In Dubroeucg et al., 4-phenylbenzo[b]thiophene-6-carboxylic acid was obtained by condensing 3-benzoylpropionic acid and 2-thiophene carboxy aldehyde in the presence of acetic anhydride and potassium acetate to obtain 5-phenyl-3-(2-thienylmethylene)-2-furanone and heating the same in acetic acid in the presence of methane sulfonic acid. Kido et al. report a method of constructing the 2,4,5,6,7,7a-hexahydrobenzofuran-2-one skeleton by the condensation reaction of 2-methyl-3-vinylbutenolide and 2-formyl-6-methyl-5-heptenic acid methyl ester and then introducing the same to furoventalene having a benzofuran skeleton isolated from sea fan (Gorgonia ventalina) (Journal of Organic Chemistry, 1981, vol. 46, pp. 4264-4266).
As described above, condensed ring compounds are useful as intermediate products for the synthesis of various medicines and agricultural agents. However, there are few general production processes for condensed ring compounds, and the development of such general production processes is much in demand. The method described above of bonding side chains of cyclic compounds having two side chains with each other often requires multiple steps for the cyclizing reaction and, accordingly, functional groups that can be introduced may sometimes be restricted depending on the reaction conditions. In addition, the availability of starting materials significantly limits the applicability of such a process as a general process for producing the various desired condensed ring compounds.
On the other hand, cycloaddition reactions, typically represented by the Dieis-Alder reaction, have a feature capable of forming a condensed ring in a single stage since two bonds are formed in the same reaction. Examples include indole alkaloid synthesis by way of indole quinodimethane type diene (Magnus et al., Tetrahedron, 1981, vol, 37, pp. 3889-3897; Journal of American Chemical Society, 1982, vol. 104, pp. 1140-1141; Journal of American Chemical Society, 1983, vol. 105, pp. 4739-4749; Journal of American Chemical Society, 1983, vol. 105, pp. 4750-4757; Journal of American Chemical Society, 1984, vol. 106, pp. 2105-2114 and Accounts of Chemical Research, 1984, vol. 17, pp. 35-41), carbazole synthesis using pyrano[3,4-b]indol-3-one or pyrano[4,3-b]indol-3-one (Doren et al., Tetrahedron, 1989, vol. 45, pp. 6761-6770; Moody et al., Journal of Chemical Society, Perkin Transaction I, 1988, pp. 1407-1415; Journal of Chemical Society, Perkin Transaction I, 1989, pp. 376-377 and Journal of Chemical Society, Perkin Transaction I, 1990, pp. 673-679), and carbazole synthesis using vinyl indole (Pindur et al., Helvetica Chimica Acta, 1988, vol. 71, pp. 1060-1064; and Journal of Organic Chemistry, 1990, vol. 55, pp. 5368-5374).
Although the above-mentioned methods are excellent in being single stage condensed ring-forming reactions, the method of Magnus et al. is only used in the intramolecular Dieis-Alder reaction, while the method of using pyranoindol-3-one or vinyl indole requires multiple stages and/or special steps for the preparation of starting materials and further requires expensive starting materials and reagents. These methods thus cannot thoroughly take advantage of the single stage cyclization reaction from an industrial point of view. Further, each of the processes is applied only to carbazole derivatives, and thus cannot be said to be a general method for synthesizing condensed ring compounds.